You will remember The Women's Health Initiative (WHI) which enrolled women in 1993 to clarify the risks and benefits of hormone replacement use. In 2002 part of the study was terminated because in the estrogen and progesterone group (Prempro in this study) there were excessive breast cancers. See
Now, we will look at the estrogen-only group. These are women who have had a hysterectomy and don't need the additional progesterone. In the WHI study, the estrogen group took conjugated equine estrogens (Premarin 0.625mg). This part of the study was terminated in 2004 because of increased stroke and leg clots. BUT, modst of the 11,000 women agreed to continued follow-up. Recently the results at 11.8 years were published for the groups taking conjugated equine estrogens for a median of 5.9 years versus the placebo group in JAMA 2011 and Lancet Oncology 2012.
The estrogen group had fewer breast cancers in the added 5 year follow-up. The estrogen group also had a reduced risk of dying from the disease.
With subgroup analysis the lower risk was only seen in the women of low or usual risk for breast cancer. The estrogen did not lower the risk in those women with a family history of breast cancer or personal history of benign breast disease. The estrogen was not protective in anyone at increased risk for getting breast cancer. The possible mechanisms at work here will be discussed in later blogs, such as timing, which estrogen or which dose.
In review then, the results allow us to further personalize our recommendations for hormone replacement. This study showed us that estrogen did increase the risk of strokes and clots, but did decrease the risk of breast cancer in certain women. These findings should reassure women who have had a hysterectomy, are at usual risk for breast cancer and seek estrogen for symptomatic menopause relief and/or bone density maintenance.
This medical content is intended for information and not personal treatment advice. These are findings to discuss with your doctor.
Together we can prevent 75,000 breast cancers each year!
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